1. Field of the Invention
The present invention is directed to a camera housing assembly and method of making the same and more particularly to a plastic camera housing assembly having an abrasion resistant metallic coating.
2. Description of the Prior Art
Camera housings have been made from diverse forms of material over the history of photography. The initial materials selected were primarily designed to provide a relatively lightweight camera structure while insuring that the interior of the camera was kept free of any undesired light. While these requirements are still germane to the present modern day camera, additional and more complex requirements have been added. The high labor cost associated with the assembling of the more expensive 35 mm cameras has required the camera manufacturers to seek alternative methods of providing housing assemblies. Heretofore, the quality required in the higher priced cameras has been met by the use of metal camera bodies. The economies presented with the use of plastic injection molding is now attracting the manufacturers of expensive cameras to switch to plastic camera housing assemblies.
Originally, cameras were made of wood and fiberboard frequently covered with cloth. Subsequently, sheet metal, aluminum and zinc die cast parts were utilized. In 1934, Eastman Kodak Company introduced their first Brownie camera molded from phenolics. Today most fixed focus cameras have become all plastic. Various types of plastic such as cellulosics, polyethylene, Nylon, phenolics, styrenes, epoxies and metacrylates have been utilized. Additionally, in the photographic field there has been suggestions to utilize high density polyethylene, high impact styrene alloy, melamine, vinyl-aluminum laminates, Nylatron (filled nylon), Fiberfil (glass-filled styrene), Delrin acetal resin and Lexan polycarbonate.
The photography industry has also attempted to utilize metal coatings on various camera component parts. For example, the Kodak Lumaclad reflector was made of a Tenite butyrate plastic shell that had been vacuum-metallized to provide a reflecting surface. For a further discussion of the use of plastics in the photography field, reference is made to Modern Plastics (April 1960) pages 102-103.
While plastic has been utilized in the relatively inexpensive fixed focus camera bodies, there has been a recognition that problems can exist with the use of plastics in the proper alignment and positioning of lenses. Various patents have suggested the use of plastic housings with a concern for the positioning of metal inserts to insure the optical centering of lenses, such as the Fay U.S. Pat. Nos. 2,559,860 and 2,559,861 and the German Auslegeschrift No. 1,147,839 (1963).
One of the acute problems that exist in converting the camera housing assemblies of the more expensive 35 mm cameras to plastic is to insure that the purchaser still perceives that he is receiving a quality product. In this regard, the use of metallized coatings on the exterior of the camera body has been suggested.
As is known, plastic has a relatively low melting point and will deform if it is heated above 300.degree. F. Preferably, the plastic camera part should not be heated above 165.degree. F. Without heating, however, it is difficult to achieve a strong adhesive coating of a metal. A further problem occurs in utilizing a vacuum since the heating of the plastic will produce various gases that will itself react and leave undesirable by-products on the surface of the camera part.
Generally, the prior art has resorted to aluminizing at a 10.sup.-3 torr vacuum where the aluminum is flash evaporated onto the plastic part. Usually the aluminum film will be about 0.1 microns and will be subsequently sandwiched between the plastic camera part and an exterior top plastic coating. The top plastic coating is usually clear, however, it can be tinted to appear as gold, silver or other decorative color.
The reflectiveness of this aluminized coating is not a duplicate of real metal because of the top protective coating of plastic. Additionally, the exterior plastic coating is not abrasion resistant. Both the exterior plastic coating and the aluminum itself is relatively soft and can be easily abraded.
Finally, the thermal conductance of the plastic coating is low compared to that of real metal and, therefore, it produces a different tactile feeling to the user of the camera.
While it has been recognized that it would be highly desirable to provide an abrasion resistant metal coating, the adhesion of a metal coating to a plastic substrate has been difficult to achieve. Again, the thermal problems dealing with the plastic has created certain barriers. The discrepancy in the coefficients of thermal expansion between metal and plastic has created cracks when the camera housing is utilized in wide extremes of ambient temperature.
Thus, there is a demand in the prior art to provide a high quality metallized plastic camera housing that will maintain the quality that camera purchasers have expected of fairly sophisticated 35 mm cameras.